T2066 Endoscopic Mucosal Resection for Undifferentiated Intramucosal Gastric Cancer: Different Indications Between Signet Ring Cell Carcinoma and Poorly Differentiated Adenocarcinoma

Abstract

Background) Small undifferentiated gastric cancer limited to the mucosal layer has been proposed as an extended indication for endoscopic mucosal resection (EMR). However, there is limited data about the difference of lymph node metastasis (LNM) in different histological subtypes between intramucosal signet ring cell carcinoma (SRC) and poorly differentiated adenocarcinoma (PDC). The aim of this study was to identify risk factors of the LNM and to suggest appropriate indications for EMR for undifferentiated intramucosal cancers. Method) We reviewed medical records of 2128 patients with intramucosal gastric cancers treated with gastrectomy and regional lymph node dissection at the Samsung Medical Center from 1994 to 2005. Clinicopathological factors related to LNM for intramucosal SRC and PDC were evaluated in comparison to differentiated intramucosal gastric cancers (DAC). Results) Out of 2128 intramucosal gastric cancers, 9 of 1243 (0.7%) cases of DAC, 20 of 594 (3.4%) cases of SRC and 18 of 291 (6.2%) cases of PDC had LNM. LNM increased significantly in SRC (OR=4.18 95% CI: 1.64-10.6) and PDC (OR=12.4 95% CI: 4.83-32.1) compared to DAC as determined by multivariate analysis. Tumor size (OR =3.36, 95% CI: 1.07-10.5) and lymphovascular invasion (OR=13.6 95% CI: 4.65-40.1) were other significant risk factors associated with LNM. None of 175 SRCs less than 20 mm in size (95% CI: 02.09) and none of 21 PDCs less than 10mm in size (95%CI: 0-16.11) without lymphovascular invasion had LNM. Conclusion) Histological subtype, tumor size and lymphovascular invasion are risk factors of LNM in undifferentiated intramucosal gastric cancers. Intramucosal SRC has an intermediate LNM risk between the differentiated type and PDC. SRCs less than 20 mm and PDCs less than 10 mm in size without lymphovascular invasion are possible candidates for EMR.